Kallus confirmed!

Regarding the Grey... Let me explain a little bit about the history of the Force as I remember it (It was a long time ago that I read it, and I'm recalling this from memory, so the details may be a little foggy). Once upon a time in a galaxy far, far away there existed (on one singular planet) a group of talented individuals who'd just begun to discover the Force and their ability to tap into it. At this point in time there were no Sith, or Jedi, or light vs Dark, there was only the grey, this group of individuals who were becoming adapt at channeling the force (both light and dark) to improve their lives and the lives of those around them. You should go and read their history, it's really quite fascinating. To sum up it up however, over time, a faction of these force wielders broke off from the others and began to forsake the light. If I remember correctly, the others strongly believed in maintaining a balance in the force between the light and the dark, and by forsaking the light, this particular faction had begun to throw off that balance which would eventually result in some serious consequences for the Galaxy. Initially the main group tried to bring this faction back in line, but that led to battles which eventually turned into wars. Over time as that faction grew stronger, the primary group of individuals concluded that in order to maintain the balance in the force that they'd have to forsake the dark. This is what eventually lead to the Sith and the Jedi orders. The efforts of these two orders created a very shaky balance that stood in jeopardy of falling apart the moment either group gained to much control, or to much power over the other. It is my opinion that the prophecy regarding bringing balance to the force had nothing to do with defeating the Dark Side or the Light Side, rather but uniting them instead. The chosen one is destined to end both the light and dark factions and to bring back the grey.

Consequently, it seems to be suggested in the last Season of Rebels (which is cannon), that Anakin was NOT the chosen one, but instead that that title had always been a reference to Luke all along. Anyone with a knowledge of the history of the force likely understood Luke's cryptic message in the SW8 trailer "It's time for the Jedi to end..." to likely be an indication that he's going to try to truly bring the force back into balance by uniting both the light and darks sides once more, and bringing back the grey order after so long a time.

Personally it is my opinion that the temple at the end of Episode 7 was the original planet and island where those individuals first discovered the force and the grey order was born. They called it the first Jedi temple in the movie, but the remnants of the Grey Order are those who formed the Jedi Order, so it stands to reason that that temple was created in the very spot where it all began.

Anyone with a greater history of these events then I do is encouraged to correct anything that I may have gotten wrong